Explosive line cutting device

ABSTRACT

An explosive line cutting device and method for clearing a fire trail. It comprises a deformable plastic explosive strand centrally disposed through a plastic tube which is substantially filled with fire-retardant solution. A booster initiator is suitably secured to one end of the explosive strand. Upon detonation of the explosive strand the solution enhances the intensity of the shock wave which clears a trail, reduces the incendiary action of the explosive charge, and at the same time provides a fire retardant effect along the fire line.

atent [191 ite States Sewell et al.

[ Aug. 20, 1974 EXPLOSIVE LINE CUTTING DEVICE [76] Inventors: Robert G. S. Sewell, 703

Ticonderoga, China Lake, Calif. 93555; Carl F. Austin, Star Rt. 1, Box 240, Inyokern, Calif. 93527 22 Filed: Oct. 21, 1971 [21] Appl. No.: 191,283

[52] US. Cl. 102/22 [51] Int. Cl. F42b 3/00, F42d 3/00 [58] Field of Search H 102/24 R, 23, 22, 97

[56] References Cited FOREIGN PATENTS OR APPLICATIONS 1,138,655 1/1969 Great Britain lO2/22 1,104,414 4/l961 Germany 102/22 Primary ExaminerSamuel Feinberg Assistant ExaminerJ. V. Doramus Attorney, Agent, or FirmR. S. Sciascia; Roy Miller; L. E. K. Pohl [5 7 ABSTRACT An explosive line cutting device and method for clearing a tire trail. It comprises a deformable plastic explosive strand centrally disposed through a plastic tube which is substantially filled with fire-retardant solution. A booster initiator is suitably secured to one end of the explosive strand. Upon detonation of the explosive strand the solution enhances the intensity of the shock wave which clears a trail, reduces the incendiary action of the explosive charge, and at the same time provides a fire retardant effect along the tire line.

3 Claims, 2 Drawing Figures Pmmimuszolm FIG. 1.

PEG. 2.

'1 EXPLOSIVE LINE CUTTINGDEVICE The invention described herein may be manufactured and used by or for the government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor BACKGROUND OF INVENTION This invention relates to an explosive fire-line cuttingdevice, and cutting method for clearing a fire trail.

Bare explosive charges have been used in clearing or cutting a line in grass, brush, or forest litter. Unfortunately, bare explosives such as a detonating fuse will. also ignite forest fuels. The problem of explosive fireline cutting is closely analogous to the problem of coal mine blasting. Deformable plastic explosive packages are well known having been used to conform to the shape of uneven surfaces or crevices which allows the explosive material to come into more intimate contact with the thing being blasted. These packages are generally sealed to keep water and other contaminants from coming in contact with the explosive charge. Detonation arresters for liquid explosives have been used which precompress an explosive to a density which creates an explosive barrier. Such devices are useful to prevent propagation of the detonation in the event of an accidental explosion. The present invention provides a rapid, safe, and effective means for blast enhancement, particularly useful in clearing fire trails. The device uses less explosive than other devices of this nature and enhances the trail effect by dispersing fire retardant along the trail as it is cleared.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a longitudinal section embodying the principles of the invention; and

FIG. 2 is a cross-sectional view of another embodiment of the invention employing multiple explosive strands.

DESCRIPTION OF THE INVENTION Referring now to the drawing there is shown in FIG. 1 a flexible length of plastic tubing having disposed through the center thereof at least one strand of plastic explosive ll. Explosive 11 is held in position in tubing 10 by a plurality of membrane-like supports 12 spaced at predetermined intervals along the inner walls of the tubing. The tubing may be of any suitable reinforced inert elastomeric material as can be the supports. Plexiglass tubing was used in the first devices made and tested herein, and wooden webbing was used for the supports to hold the strand in place. Multiple strands of explosive as shown in FIG. 2 were also used. The space in the tubing surrounding the strand is substantially filled with an aqueous fire-retardant solution designated generally by numeral Theends of tubing;

are sealed by crimping or other means to prevent the loss of the solution containing the fire retardant. A booster initiator 14 is positioned at one end of explosive l1 and placed so as to extend beyond the end of tubing 10 for ignition purposes. The explosive strand used was a pentaerythritol tetranitrate (PETN) filled detonating fuse and a diammonium phosphate mixture was the fire retardant. Other deformable explosives reliable and safe in the 400 to 1,200 grain per foot size could be used as could any of the commercial fire retardants, or simply water per se.

In operation the tube containing the explosive core or strand is unreeled and deployed at any desired length and in any desired configuration in the area to be cleared. The solution consisting essentially of fireretardant and water or just water is pumped into the tube 10 which is closed at both ends. A booster initiator 14 is positioned at one end of explosive strand 11. Upon detonation of the booster initiator and thereafter the explosive strand, a line is cut through the adjacent vegetation providing quick access to the area. This device in operation normally provides a fireline that is two to three feet in width. The water-fire retardant solution enhances the blast effect and acts to widen the path. The fire-retardant in the solution limits further ignition of the surrounding vegetation.

The present invention provides a device which rapidly and safely clears fire lines of brush and low scrubby growth. The solution surrounding the explosive core provides blast enhancement; less explosive is needed; fewer personnel are needed to deploy and operate the device; and, the retardant limits further ignition of the surrounding growth.

What is claimed is:

l. A rapid fire line cutting device which comprises:

a plastic tube of predetermined size provided with web-like support structure extending from the inner walls toward the center of the tube;

means for sealing the ends of said tube;

at least one defonnable explosive strand disposed through the center of the tube and being supported therein by said web-like support;

an aqueous solution surrounding said explosive strand; and

a booster initiator positioned at one end of said strand.

2. The device in accordance with claim 1 wherein the plastic tube is plexiglass and the explosive strand is pentaerythritol tetranitrate.

3. The device in accordance with claim 2 wherein the aqueous solution comprises water and diammonium hpsp 

1. A rapid fire line cutting device which comprises: a plastic tube of predetermined size provided with web-like support structure extending from the inner walls toward the center of the tube; means for sealing the ends of said tube; at least one deformable explosive strand disposed through the center of the tube and being supported therein by said web-like support; an aqueous solution surrounding said explosive strand; and a booster initiator positioned at one end of said strand.
 2. The device in accordance with claim 1 wherein the plastic tube is plexiglass and the explosive strand is pentaerythritol tetranitrate.
 3. The device in accordance with claim 2 wherein the aqueous solution comprises water and diammonium phosphate. 